This invention relates to methods for making metal cyanide catalysts complexes and to methods for polymerizing alkylene oxides in the presence of a metal cyanide catalyst.
Polyethers are prepared in large commercial quantities through the polymerization of alkylene oxides such as propylene oxide and ethylene oxide. This polymerization reaction is usually conducted in the presence of an initiator compound and a catalyst. The initiator compound usually determines the functionality (number of hydroxyl groups per molecule of the polymer) and in some instances imparts some desired functionality. The catalyst is used to provide an economical rate of polymerization.
Metal cyanide complexes are becoming increasingly important alkylene oxide polymerization catalysts. These complexes are often referred to as “double metal cyanide” or “DMC” catalysts, and are the subject of a number of patents, including, for example, U.S. Pat. Nos. 3,278,457, 3,278,458, 3,278,459, 3,404,109, 3,427,256, 3,427,334, 3,427,335 and 5,470,813, among many others. In some instances, these complexes provide the benefit of fast polymerization rates and narrow polydispersities. Additionally, these catalysts are associated with the production of polyethers having very low levels of monofunctional unsaturated compounds.
It is often desirable to remove residual DMC catalyst from polyethers. Various methods of accomplishing this have been developed, but the simplest method would be a simple filtration or phase separation. However, DMC catalysts that can be easily and effectively filtered from the polyol have not been commercially established.
Thus, it would be desirable to provide metal cyanide catalyst complex that exhibits good catalytic activity and can be simply and easily removed from a polyether polyol.